Saturday, 23 March 2013

Basic Techniques: Contours and Alpha Curves

In this tutorial i will show you a
technique that will bring your texteffects to the next level.

In Photoshop its called 'Contours' and
an essential part of 'Layer Style'.

Almost anything done with Contours
in PS can be imitated in Gimp with Curves.

There is a script called 'layerfx' by Jonathan Stipe.
It imitates most functions PS Layer Style has.
This script will not turn your Gimp into Photoshop, as Layer Style is far more sophisticated, but it does a pretty good job at helping you, making complex texteffects easily.

Also note that you cant translate PS tutorials 1:1 into Gimp.
You can use PS tutorials and try to imitate the effects with layerfx, but its not an easy task !

I recommend the Python version over the .scm, because the Python has a preview.
(Put py-script into your Plug-ins User-folder !)

layerfx has its Contours under the name of 'Surface Contour' and 'Gloss Contour'.
These Curves are all pre-programmed and cannot be changed.

While layerfx is a great script it has some flaws:
The Stroke is crap (jagged edges).
Also there are some bugs:
sometimes the History/Undo is killed by the script, meaning your history is gone and Undo is greyed out.
So its always a good idea to save your project before you use it.

The latest version of layerfx makes use of layergroups which is basically a good idea, but strangely enough, modes dont seem to work as long layers are inside the folder.
You have to drag your layers out and then delete the folder. After that everything should look like its supposed to.

But now lets start with the tutorial !

Fill an elliptical selection with a
colour of your choice. The layer must be transparent !

After deselecting, apply a Gaussian
Blur of 50.

Call up the 'Curves Tool' under
'Colours'. Next to 'Channel' is a dropdown menu.

As a default its set to 'Value' but for this technique to work, you
have to set it to Alpha ! This is essential.

The Alphachannel represents
transparency.

Manipulating the curve, tweaks the
blur.Drag the curve up and the blur expands. Drag it down, and the blur shrinks.

This can be used for tweaking all kind
of blurred objects, like an Inner Glow or an Inner Shadow.

So in case you didnt chose a perfect
blur for your layereffect, you can tweak it with an alphacurve.This gives you a lot of control !

An other application is when using Gradients.

Fill a transparent layer with a gradient FG to Transparent. Drag it from top to bottom with the 'Adaptive Supersampling' box checked - this will give you the best gradient possible.

Now drag the curve up and down and watch how the gradient spreads or retracts.With this trick you can customshape your gradient any way you like.

But this is only the beginning.

We
can give our curve a much more complex shape, and tweak the
appearance of the blur/gradient into ring and step-like shapes like this:

or this (wild curves on a radial gradient):

In Photoshop you
have 12 Contours,

and each one has a different name, which describes
the effect.These
Contours can be displayed with little diagrams as in this chart and
what you see is a cross chart of the final effect and at the same
time, the shape of the curve.

You
dont have to give the curve the exact same shape, something similar
is good enough to get the same effect and you can tweak your curve
and the blur by adding more anchors and playing with them.

A very obvious
application of these effects is of course giving your Outer Glow the
appearance of a ring-like aura, like this:

But you can even
do more than that. Use a contoured shape as a map for your
BumpMap script. This is what the 'Surface Contour' in layerfx does.

Getting above effect by hand, works by selecting your basetext, filling the selection on a new
transparent layer with white and after deselecting, applying Gaussian Blur.

Then shape the map with a contour and use this layer as the bumpmap.

We can also render
the bevel highlights and shades by running the 'Colour to Alpha' filter on
the bumpmapped layer. After that you can shape them even further with a
curve.

I always use a 50
grey (#808080) for my basetext to make this process even easier. Its a
good colour for applying a bumpmap and you can memorize the value
easily, when you want to use 'Colour to Alpha'.

When you use
layerfx for making a bevel, you automatically get seperate layers for
highlights and shadows and you can also select a contour in the
script, called the 'Gloss Contour'.

An example for a
shaped Gloss Contour can be seen here:

I made a bevel in
layerfx with the 'Surface Contour': 'Cone'.

Afterwards i
tweaked the Gloss Contour with the Curves Tool into a freehand ringlike shape, which gave me this glossy laquer effect.

To conclude this
tutorial i will show you a chart with the 10 Contours applied to a
Glow.